Styrene-based resins are used in extensive fields including electric and electronic apparatuses, automobiles, machine parts, miscellaneous goods and other various applications owing to their excellent mechanical properties, moldability and appearance. However, since styrene-based resins are poor in impact strength and heat resistance, proposed are various techniques such as adding a soft ingredient like rubber for improving impact strength, and adding a resin having a high glass transition temperature or a crystalline resin for improving heat resistance.
Above all, as methods for improving the toughness and heat resistance of styrene-based resins, many polymer blends with polycarbonate resins are proposed. However, polymer blends consisting of styrene-based resins and polycarbonate resins have problems that the mechanical properties, moldability and appearance as features of styrene-based resins are lowered, since the miscibility between styrene-based resins and polycarbonate resins are low.
So, as methods for solving these problems, proposed are a method of adding an epoxy modified/acid modified diene-based block copolymer as a miscibilizing agent to a polycarbonate-based resin and a polystyrene-based resin (patent document 1), a method of adding a block or graft copolymer consisting of two or more of an aromatic vinyl monomer, carbonate monomer and acrylic monomer, to a syndiotactic polystyrene-based resin and an aromatic polycarbonate resin (patent document 2), a method of adding a graft copolymer having a multiphase structure consisting of polycarbonate-based resin segments and epoxy group-containing a vinyl-based polymer segment, to one or more of a polycarbonate-based resin, polyester-based resin, polyamide-based resin and polyarylene sulfide-based resin, and a styrene-based resin (patent document 3), and a method of adding a copolymer consisting of an aromatic vinyl having an intrinsic viscosity of 1.5 dl/g or more and a weight average molecular weight/number average molecular weight ratio of more than 3.0 and vinyl cyanide, to a thermoplastic resin such as a polycarbonate resin or polyester resin, for enhancing melt moldability. However, even if any of the resins obtained by the inventions described in these patent documents is melt-kneaded or melt-blended using an extruder or the like and subsequently molded by a general method such as injection molding or blow molding, the miscibility with the styrene-based resin is not sufficiently enhanced, and a regular wavelength of concentration fluctuation cannot be formed without giving any sufficient effect of improving toughness.
Furthermore, in the case where a styrene-based resin and a polycarbonate resin are alloyed, chemicals resistance declines, and as a method for preventing it, the amount of vinyl cyanide such as acrylonitrile is increased. However, this method causes such problems that the miscibility with the polycarbonate is lowered and further that the melt processability is also lowered. As methods for solving the problems, disclosed are a method in which the sequential amount of the three acrylonitrile molecules to be cyclized during melt processing is specified (patent document 5) and a method of adding two specific ABS-based resins different in the amount of vinyl cyanide, to a polycarbonate resin (patent document 6). However, the obtained resin compositions do not allow a sufficient chemicals resistance effect to be obtained unless the amount of vinyl cyanide in the composition is larger than a certain amount, and are also unsatisfactory in mechanical properties and moldability.
A polymer alloy consisting of two or more resins separated in phase by spinodal decomposition, having a co-continuous structure with a wavelength of concentration fluctuation of 0.01 to 1 μm or a dispersed structure with a distance between particles of 0.01 to 1 μm (patent document 7), is disclosed. However, the polymer alloy described in the patent document has said structure obtained by melt blending and subsequent special press molding, and if it is simply molded by a general molding method such as injection molding, the wavelength of concentration fluctuation becomes too large during molding, not allowing excellent physical properties obtained. Furthermore, said phase structure cannot be obtained stably.
In the case where a rubber as a component, another resin, filler and the like are added to a styrene-based resin for melt blending, there are such problems that the properties of the styrene-based resin are greatly lowered due to the miscibility between the components, dispersibility, thermal deterioration depending on conditions, etc. As methods for solving the problems, disclosed are a method in which a powdery thermoplastic resin containing a large amount of a rubber as a component is extruded as a strand to form grains using a single-screw extruder having an L/D of 7.8 to 16 and a screw compression ratio of 1.4 to 2, with the pressure difference between the tip of the extruder and the inlet to the die kept at 0.3 Pa or less, at a resin temperature of 120 to 160° C. immediately before the die portion and at a resin pressure of 1.0 to 3.0 MPa (patent document 8), and a method in which organophilic clay and a polymer are melt-blended with the reduced pressure on the resin kept in a certain range in a filled region and with the total shear strain and/or the total shear energy per unit area kept in a certain range (patent document 9). However, if the said manufacturing methods are used for the polymer alloy of the present application, homogeneous melt blending is difficult and the heat generation caused by a high resin pressure under high shear flow thermally deteriorates the polymer of the present application, to greatly lower the mechanical properties. So, it is desired to further improve the manufacturing methods.
Furthermore, proposed is a resin composition for plating, consisting of a polycarbonate resin and acrylonitrile-butadiene-styrene resin (hereinafter called ABS resin), wherein the weight average molecular weight of the acetone-soluble matter in the ABS is 100,000 or more and the vinyl cyanide monomer content in the acetone soluble matter is 15 to 32 wt % (patent document 10). However, said patent document does not describe at all about the improvement of mechanical properties, etc. using a miscibilizing agent. Further, it neither describes nor suggests that if a regular wavelength of concentration fluctuation is formed, excellent plating properties can be exhibited.    [Patent Document 1] European Patent No. 893476    [Patent Document 2] JP2004-210916A (Pages 2-3)    [Patent Document 3] JP11-080287A (Page 2)    [Patent Document 4] JP11-080470A (Pages 2 and 4)    [Patent Document 5] JP9-059464A (Pages 2 and 4-5)    [Patent Document 6] JP2001-131398A (Page 2)    [Patent Document 7] JP2003-286414A (Pages 2 and 15-17)    [Patent Document 8] JP2003-136526A (Page 2)    [Patent Document 9] U.S. Pat. No. 6,472,460    [Patent Document 10] JP10-046019A (Page 2)